Guo Dong, Yi Hong-Yan, Li Hui-Liang, Liu Chen, Yang Zi-Ping, Peng Shi-Qing
Key Laboratory of Biology and Genetic Resources of Tropical Crops, Ministry of Agriculture, Institute of Tropical Bioscience and Biotechnology, Chinese Academy of Tropical Agricultural Sciences, Haikou, 571101, China.
Plant Cell Rep. 2015 Sep;34(9):1569-78. doi: 10.1007/s00299-015-1809-6. Epub 2015 May 19.
The HbCZF1 protein binds to the hmg1 promoter in yeast and this interaction was confirmed in vitro. The hmg1 promoter was activated in transgenic plants by HbCZF1. Biosynthesis of natural rubber is known to be based on the mevalonate pathway in Hevea brasiliensis. The final step in the mevalonate production is catalyzed by the branch point enzyme, 3-hydroxy-3-methyl-glutaryl coenzyme A reductase (HMGR), which shunts HMG-CoA into the isoprenoid pathway, leading to the synthesis of natural rubber. However, molecular regulation of HMGR expression is not known. To study the transcriptional regulation of HMGR, the yeast one-hybrid experiment was performed to screen the latex cDNA library using the hmg1 (one of the three HMGR in H. brasiliensis) promoter as bait. One cDNA that encodes the CCCH-type zinc finger protein, designated as HbCZF1, was isolated from H. brasiliensis. HbCZF1 interacted with the hmg1 promoter in yeast one-hybrid system and in vitro. HbCZF1 contains a 1110 bp open reading frame that encodes 369 amino acids. The deduced HbCZF1 protein was predicted to possess a typical C-X7-C-X5-C3-H CCCH motif and RNA recognition motif. HbCZF1 was predominant in the latex, but little expression was detected in the leaves, barks, and roots. Furthermore, in transgenic tobacco plants, over-expression of HbCZF1 highly activated the hmg1 promoter. These results suggested that HbCZF1 may participate in the regulation of natural rubber biosynthesis in H. brasiliensis.
HbCZF1蛋白在酵母中与hmg1启动子结合，且这种相互作用在体外得到了证实。HbCZF1在转基因植物中激活了hmg1启动子。已知巴西橡胶树天然橡胶的生物合成基于甲羟戊酸途径。甲羟戊酸生成的最后一步由分支点酶3-羟基-3-甲基戊二酰辅酶A还原酶（HMGR）催化，该酶将HMG-CoA分流到类异戊二烯途径，从而导致天然橡胶的合成。然而，HMGR表达的分子调控尚不清楚。为了研究HMGR的转录调控，进行了酵母单杂交实验，以巴西橡胶树中hmg1（三种HMGR之一）启动子为诱饵筛选乳胶cDNA文库。从巴西橡胶树中分离出一个编码CCCH型锌指蛋白的cDNA，命名为HbCZF1。HbCZF1在酵母单杂交系统和体外均与hmg1启动子相互作用。HbCZF1包含一个1110 bp的开放阅读框，编码369个氨基酸。推导的HbCZF1蛋白预计具有典型的C-X7-C-X5-C3-H CCCH基序和RNA识别基序。HbCZF1在乳胶中占主导地位，但在叶片、树皮和根中几乎检测不到表达。此外，在转基因烟草植物中，HbCZF1的过表达高度激活了hmg1启动子。这些结果表明，HbCZF1可能参与了巴西橡胶树天然橡胶生物合成的调控。
